Re: Active/Active/Active/Passive and Database Mirroring

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You can have however many instances you want as long as you have enough
resoruces (disks, IPs, and network names).

It's a reasonable design in a four-node cluster to have three SQL2005
instances, each of which runs on a separate node and the 4th node is left as
a spare.

In addition to configuring where the instances should normally run, you also
need to plan/configure the failover behavior. For instane, one design would
be for the instance on Node A to failover only to Node D, and do the same
for the instances on Node B and Node C. In other words, you designate Node D
to be the only and common spare. This design would not give you any HA if
Node D fails. But you may consider that as by design. And if this is no good
for your requirements, choose a different design. The point is that you need
to be explicit about the failover behavior, and communicate that to the
users so that hopefully they know what to expect.

FWIW, I usually call this a N+1 cluster following the Unix tradition, where
N is the umber of 'active nodes' and 1 is the spare.
'Active/Active/Active/Passive' is just too mouthful.

Linchi


"Chad T" <ChadT@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:EEF10540-FCF0-4411-AFC0-44ECDE2B6BFD@xxxxxxxxxxxxxxxx
Just so I understand this correctly, if we go with an
Active/Active/Active/Passive cluster we would have a setup of at least
this,
correct?
Is the minimum number of instances in this configuration 3?

Ex2: (4 nodes - 1 passive = 3 instances split over 3 nodes )
Node A = Instance1
Node B = Instance2
Node C = Instance3
Node D = Passive



"Geoff N. Hiten" wrote:

SQL Clustering is a failover technology only. It does not load-balance.

--
Geoff N. Hiten
Senior Database Administrator
Microsoft SQL Server MVP



"Chad T" <ChadT@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:DC9DA36B-0D19-4E7E-9CD8-03F3A71F389B@xxxxxxxxxxxxxxxx
Thank you for such a fast response.
In the active/active/active/passive configuration is it possible to
load
balance the 3 instances over 3 nodes?

Ideally we would like to create 1 instance split over 3 nodes... is
this
possible (see EX1) or do we have to do something like EX2?

Ex1: (1 instances - share over 3 nodes)
Node A = Instance1 (load balanced)
Node B = Instance1 (load balanced)
Node C = Instance1 (load balanced)
Node D = Passive

Ex2: (4 nodes - 1 passive = 3 instances split over 3 nodes)
Node A = Instance1 (load balanced)
Node B = Instance2 (load balanced)
Node C = Instance3 (load balanced)
Node D = Passive


"Geoff N. Hiten" wrote:

Instances are installed to the entire cluster, but can be set to
prefer
certain nodes. I personally like N-1 clusters (N nodes, N-1
Instances),
just to simplfy management, but other that is not an absolute,
inflexible
standard.

Each instance has completely separate resources; IP address, Data
disks,
Log
Disks, TempDB, and Network Name. Each instance works and appears as a
separate and distinct SQL Server.

--
Geoff N. Hiten
Senior Database Administrator
Microsoft SQL Server MVP



"Chad T" <ChadT@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:B13AE62F-89A3-405F-9F14-FE979336CC7B@xxxxxxxxxxxxxxxx
We have 4 systems that was initially planned to be joined into an
Active/Active/Active/Passive cluster with SQL 2005.

Can anyone offer a suggestion on the number of instances to install
per
node?
Does each instance need seperate Disks for the Database, Logs and
TempDB?
If we stay with this configuration will Database mirroring still be
an
option with the configuration once it is supported by MS.









.

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